DIETARY KRILL MEAL INCLUSION RESULTS IN HIGHEST GROWTH PERFORMANCE OF JUVENILE WHITELEG SHRIMP Litopenaeus vannamei WHEN COMPARED TO OTHER FEED ATTRACTANTS
Feed attractants are widely used in shrimp feeds to stimulate feed intake and enhance their growth performance. The present study aimed at investigating the effect of marine feed attractants on the growth stimulation of whiteleg shrimp, L. vannamei. The following marine ingredients were evaluated: dried shrimp meal (DSM), shrimp head meal (SHM), squid meal (SQM), squid liver meal (SLM), krill meal (KRM), and sardine hydrolysate (SAH). Salmon meal and soy protein concentrate were used as positive (POS) and negative (NEG) controls, respectively. All dried ingredients were incorporated into a similar formula, at 3.0% dietary inclusion (as-is, basis), except SAH (liquid) added at 5.0%. The basal formula consisted of a low fishmeal diet containing only 3.0% and 2.7% salmon meal and oil, respectively, as marine ingredients. A total of 56 outdoor tanks of 1 m3 were used in this study, allowing seven replicate tanks per dietary treatment. Juvenile L. vannamei of 0.99 ± 0.08 g (n = 5,712) were stocked at 100 shrimp/m2 and fed 10 times daily from 07:00 am to 05:00 pm with an automatic feeder. Feed rations were adjusted bi-weekly by weighing 10 shrimp from each tank. Harvest took place after 74 days of rearing. Mean (± SD) water salinity, pH and temperature reached 34 ± 2 g/L (n = 3,078), 7.95 ± 0.16 (n = 3,079), and 30.0 ± 1.0oC (n = 3,077). Final shrimp survival reached 93.3 ± 5.8% and was unaffected by dietary treatment (P > 0.05). Shrimp fed SAH resulted in the lowest weekly growth rate at 0.86 ± 0.10 g compared to KRM with the highest at 1.04 ± 0.09 g (P < 0.05). Gained shrimp yield was significantly higher for shrimp fed KRM (1,037 ± 73 g/m2) and POS (28 ± 40 g/m2) compared to all other treatments. Final shrimp body weight exceeded 10 g at harvest with the highest for those fed KRM (11.97 ± 1.79 g), followed by POS (11.11 ± 1.55 g) and SQM (11.01 ± 1.83 g). Feed conversion ratio (FCR) was statistically lower for shrimp fed KRM (1.31 ± 0.05) when compared to other diets, except when compared to SQM (1.41 ± 0.07), POS (1.42 ± 0.05), and NEG (1.44 ± 0.07). The lowest amount of feed was delivered in tanks fed SAH (12.5 ± 0.7 g/shrimp), SHR (12.6 ± 0.6 g/shrimp), and NEG (12.6 ± 0.3 g/shrimp) compared to the highest with KRM (13.6 ± 0.6 g/shrimp). Data indicate that shrimp fed diets containing 3% KRM grows faster, achieves a higher body weight with a lower FCR and higher yield compared to diets with other marine feed attractants. Feeds containing 5% SAH leads to the poorest growth performance in whiteleg shrimp even when compared to a NEG control. In conclusion, shrimp fed KRM performs better than other marine feed attractants due to its higher nutrient value and attractability.
